Fiber-optic based digital intercommunication systems have been provided for handling communications on multiple-operator platforms, such as aircraft. Operators interacting with audio at various levels of security classification or importance (i.e., cross-domain interactions) require equipment that will allow them to listen to audio at a variety of security levels simultaneously and to talk on one selected security level while ensuring isolation between the audio streams and meeting Information Assurance requirements. Conventional digital intercommunication systems have been provided that attempt to handle multi-level security (MLS) audio communications to allow simultaneous connection to multiple networks at different security levels. Some systems utilize software running on a single software-programmable CPU to mix the audio and to manage the control of the system. Other audio products exist that attempt to implement multiple levels of audio processing by using a single, isolated system for each processing level (Multiple Independent Level Security, MILS). Some products also enforce separation of audio data from control data. Mixing in hardware is sometimes employed to maintain channel separation and to provide multiple levels of security. Other security-relevant systems regularly employ the use of security “tags” onto data to identify or specify the security level of specific items or piece of data as it travels through a system or device. Systems allowing transmission of data between multiple levels of security are commonly referred at Cross Domain Solutions (CDS).
Government agencies may levy requirements on CDS to ensure the separation of data at multiple levels security, for example, to provide MLS security during joint service and coalition (multi-nation) operations where various audio classification levels are used, permitting side by side personnel to have audio communications (e.g., to listen to audio at a variety of levels simultaneously and to talk on one selected level while ensuring isolation between the audio streams) at restricted levels without the worry of information being compromised.